Abstract
WE notice in the last number of the Izvestia of the East Siberian Geographical Society (vol. xix. 1), a most interesting note, by L. A. Jaczewski, on the geological results of the last Sayan expedition. The immense border-ridge of the great plateau of East Asia, which stretches from the sources of the lya to Lake Baikal, was very little known. Many explorers have visited the valleys of the Irkut and Oka which flow at its northern base, but very few have crossed it, and if they crossed the huge ridge, it was mostly to the north of Lake Kosogol, where a broad passage is opened from the lowlands to the high plateau. The Expedition of MM. Prein and Jaczews crossed it at three different places, and thus obtained an insight into its geological structure. As to its age, it appears that limestones, most probably Silurian, lie almost undisturbed at its northern base, so that the hypothesis as to the great plateau having been a continent since the Laurentian or Huronian epochs is thus confirmed. We notice also that, besides Munku Sardyk, 3500 metres high, there are in the Sayan at least three or four summits of nearly the same height; and that, viewed from the south on the banks of the Kirlygoi stream, it appears as a massive wall, 700 metres high, having a direction from the north-west to the south-east. As to the complex ramifications of the Sayan, they are chiefly due to a most extensive action of atmospheric agencies, as was foreseen by Tchersky. Most interesting observations were made as to the formerly quite unknown glaciers of the northern slope, where they have the shape of narrow glaciers descending down a very steep slope and taking their origin amidst wide snow-fields. Their lower extremities reach a lower level than on the southern slopes. As to the former extension of glaciers, which was maintained by Kropotkin, but doubted on account of prevailing theoretical conceptions as to the non-glaciation of Siberia, M. Jaczewski found plenty of striae and striated boulders which made him consider that glaciers formerly extended to a level of 1500 metres on the northern slope, and 1700 metres on the southern slope turned towards the plateau.
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Geographical Notes . Nature 38, 577 (1888). https://doi.org/10.1038/038577b0
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DOI: https://doi.org/10.1038/038577b0